U.S. patent number 7,914,196 [Application Number 12/054,680] was granted by the patent office on 2011-03-29 for light redirecting film systems having pattern of variable optical elements.
This patent grant is currently assigned to Rambus International Ltd.. Invention is credited to Robert M. Ezell, Timothy A. McCollum, Jeffery R. Parker.
United States Patent |
7,914,196 |
Parker , et al. |
March 29, 2011 |
Light redirecting film systems having pattern of variable optical
elements
Abstract
Light redirecting film systems comprise a backlight having
deformities that cause a majority of the light entering the input
edge of the backlight to be emitted from a light output surface of
the backlight. In close proximity to the light output surface is a
light redirecting film that has a pattern of individual optical
elements of well-defined shape to redistribute the light emitted by
the light output surface toward a direction normal to the film.
Inventors: |
Parker; Jeffery R. (Richfield,
OH), McCollum; Timothy A. (Avon Lake, OH), Ezell; Robert
M. (Brunswick, OH) |
Assignee: |
Rambus International Ltd.
(KY)
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Family
ID: |
25427020 |
Appl.
No.: |
12/054,680 |
Filed: |
March 25, 2008 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20080239755 A1 |
Oct 2, 2008 |
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Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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11484063 |
Jul 11, 2006 |
7364342 |
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10729113 |
Aug 15, 2006 |
7090389 |
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09909318 |
Jun 22, 2004 |
6752505 |
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09256275 |
Mar 30, 2004 |
6712481 |
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Current U.S.
Class: |
362/618; 385/131;
362/624; 349/65; 362/627 |
Current CPC
Class: |
G02B
6/0068 (20130101); G02B 6/0053 (20130101); F21V
5/10 (20180201); A61M 21/02 (20130101); G02B
6/0061 (20130101); G02B 6/0065 (20130101); G02B
6/0018 (20130101); G02B 6/002 (20130101); G02B
6/0036 (20130101); F21V 11/00 (20130101); G02B
6/0021 (20130101); G02B 6/0038 (20130101); G02B
6/0043 (20130101); H01H 2219/062 (20130101); A61N
2005/063 (20130101); G02B 6/006 (20130101); H01H
2221/07 (20130101); A61B 2090/309 (20160201); A61M
2021/0044 (20130101); G02B 6/0028 (20130101); A61N
2005/0652 (20130101); G02B 6/0031 (20130101); A61N
5/0621 (20130101) |
Current International
Class: |
F21V
7/04 (20060101) |
Field of
Search: |
;362/615,618,619,620,624,625,626,606,608,627 ;385/131
;349/65,69,70 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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10-068803 |
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Mar 1998 |
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JP |
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10-319216 |
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Dec 1998 |
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JP |
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2000-280267 |
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Oct 2000 |
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JP |
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2001-166113 |
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Jun 2001 |
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JP |
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WO 96/27757 |
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Sep 1996 |
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WO |
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WO 98/50806 |
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Nov 1998 |
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WO |
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WO 99/42861 |
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Aug 1999 |
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WO |
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WO 01/27527 |
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Apr 2001 |
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WO |
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WO 01/27663 |
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Apr 2001 |
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WO |
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Primary Examiner: Negron; Ismael
Attorney, Agent or Firm: Renner, Otto, Boisselle &
Sklar, LLP
Parent Case Text
CROSS-REFERENCE TO RELATED APPLICATIONS
This application is a division of U.S. patent application Ser. No.
11/484,063, filed Jul. 11, 2006, which is a division of U.S. patent
application Ser. No. 10/729,113, filed Dec. 5, 2003, now U.S. Pat.
No. 7,090,389, which is a division of U.S. patent application Ser.
No. 09/909,318, filed Jul. 19, 2001, now U.S. Pat. No. 6,752,505,
which is a continuation-in-part of U.S. patent application Ser. No.
09/256,275, filed Feb. 23, 1999, now U.S. Pat. No. 6,712,481, the
entire disclosures of which are incorporated herein by reference.
Claims
What is claimed is:
1. A light redirecting film system comprising a backlight including
at least one input edge for receiving light from a light source,
and at least one light output surface for emitting light, the
backlight having deformities that cause most of the light entering
the input edge to be emitted from the light output surface at
relatively low angles, and a light redirecting film in close
proximity to the light output surface for receiving light emitted
from the light output surface, the light redirecting film having a
pattern of individual optical elements of well-defined shape that
vary at different locations on the film to redistribute the light
emitted from the light output surface toward a direction normal to
the film.
2. The system of claim 1 wherein the deformities of the backlight
cause most of the light to be emitted from the light output surface
at angles substantially greater than ninety degrees away from the
input edge.
3. The system of claim 1 wherein the size or shape of the optical
elements are tailored to redistribute more of the light emitted
from the light output surface of the backlight within a desired
viewing angle.
4. The system of claim 1 wherein at least some of the optical
elements are oriented at different angles.
5. The system of claim 1 wherein at least some of the optical
elements have different slope angles.
6. The system of claim 1 wherein at least some of the optical
elements are oriented at different angles across the film to
redistribute the light along two different axes.
7. The system of claim 1 wherein the size of at least some of the
optical elements varies across the film.
8. The system of claim 1 wherein the density of the optical
elements varies across the film.
9. The system of claim 1 wherein the optical elements comprise
depressions in or projections on the film.
10. The system of claim 1 further comprising a liquid crystal
display in close proximity to the film, wherein the variations in
the pattern of optical elements on the film cause a change in angle
of a light ray output distribution from the light output surface to
make the light ray output distribution more acceptable to travel
through the liquid crystal display.
11. The system of claim 1 wherein the optical elements on the film
are randomized in size, shape, position, depth, orientation, angle
or density.
12. The system of claim 1 wherein at least some of the optical
elements include a combination of planar and curved surfaces.
13. The system of claim 12 wherein the ratio of the areas of the
planar and curved surfaces is selected to produce a desired viewing
angle.
14. The system of claim 1 wherein at least some of the optical
elements overlap each other.
15. The system of claim 14 wherein at least some of the optical
elements intersect each other.
16. The system of claim 14 wherein at least some of the optical
elements interlock each other.
17. The system of claim 14 wherein at least some of the optical
elements are staggered with respect to each other.
18. The system of claim 1 wherein the deformities of the backlight
partially collimate light along one axis, and the optical elements
of the film partially collimate the light emitted by the backlight
along another axis perpendicular to the one axis.
19. The system of claim 18 wherein at least some of the optical
elements are quite small in relation to the width and length of the
film and differ in size or shape to redistribute more of the light
emitted by the backlight.
20. The system of claim 18 wherein at least some of the optical
elements are oriented at different angles relative to each other to
redistribute more of the light emitted by the backlight within a
desired viewing angle.
21. The system of claim 18 wherein at least some of the optical
elements are randomly distributed across the film.
22. A light redirecting film system comprising a backlight
including at least one input edge for receiving light from a light
source, and at least one light output surface for emitting light,
the backlight having individual optical deformities of well-defined
shape for causing 60 to 70% or more of the light received through
the input edge to be reflected or refracted out of the light output
surface, and a light redirecting film in close proximity to the
light output surface for receiving light emitted from the light
output surface, the light redirecting film having a pattern of
individual optical elements of well-defined shape to redistribute
the light emitted by the backlight toward a direction normal to the
film.
23. The system of claim 22 wherein at least some of the deformities
have rounded side walls for scattering the light in different
directions within the backlight before the light is reflected or
refracted out of the one output surface of the backlight.
24. The system of claim 22 wherein a plurality of focused light
sources are positioned in laterally spaced relation along the input
edge.
25. The system of claim 24 wherein the focused light sources are
LEDs.
Description
FIELD OF THE INVENTION
This invention relates to light redirecting films and film systems
for redirecting light from a light source toward a direction normal
to the plane of the films.
BACKGROUND OF THE INVENTION
Light redirecting films are thin transparent or translucent optical
films or substrates that redistribute the light passing through the
films such that the distribution of the light exiting the films is
directed more normal to the surface of the films. Heretofore, light
redirecting films were provided with prismatic grooves, lenticular
grooves, or pyramids on the light exit surface of the films which
changed the angle of the film/air interface for light rays exiting
the films and caused the components of the incident light
distribution traveling in a plane perpendicular to the refracting
surfaces of the grooves to be redistributed in a direction more
normal to the surface of the films. Such light redirecting films
are used, for example, with liquid crystal displays, used in laptop
computers, word processors, avionic displays, cell phones, PDAs and
the like to make the displays brighter.
The light entrance surface of the films usually has a transparent
or matte finish depending on the visual appearance desired. A matte
finish produces a softer image but is not as bright due to the
additional scattering and resultant light loss caused by the matte
or diffuse surface.
Heretofore, most applications used two grooved film layers rotated
relative to each other such that the grooves in the respective film
layers are at 90 degrees relative to each other. The reason for
this is that a grooved light redirecting film will only
redistribute, towards the direction normal to the film surface, the
components of the incident light distribution traveling in a plane
perpendicular to the refracting surfaces of the grooves. Therefore,
to redirect light toward the normal of the film surface in two
dimensions, two grooved film layers rotated 90 degrees with respect
to each other are needed, one film layer to redirect light
traveling in a plane perpendicular to the direction of its grooves
and the other film layer to redirect light traveling in a plane
perpendicular to the direction of its grooves.
Attempts have been made in the past to create a single layer light
redirecting film that will redirect components of the incident
light distribution traveling along two different axes 90 degrees to
each other. One known way of accomplishing this is to provide a
single layer film with two sets of grooves extending perpendicular
to each other resulting in a pyramid structure which redirects
light traveling in both such directions. However, such a film
produces a much lower brightness than two film layers each with a
single groove configuration rotated 90 degrees with respect to each
other because the area that is removed from the first set of
grooves by the second set of grooves in a single layer film reduces
the surface area available to redirect light substantially by 50%
in each direction of travel.
In addition, heretofore, the grooves of light redirecting films
have been constructed so that all of the grooves meet the surface
of the films at the same angle, mostly 45 degrees. This design
assumes a constant, diffuse angular distribution of light from the
light source, such as a lambertian source, a backlighting panel
using a printing or etching technology to extract light, or a
backlighting panel behind heavy diffusers. A light redirecting film
where all of the light redirecting surfaces meet the film at the
same angle is not optimized for a light source that has a
nonuniform directional component to its light emission at different
areas above the source. For example, the average angle about which
a modern high efficiency edge lit backlight, using grooves or
micro-optical surfaces to extract light, changes at different
distances from the light source, requiring a different angle
between the light redirecting surfaces and the plane of the film to
optimally redirect light toward the normal of the film.
There is thus a need for a light redirecting film that can produce
a softer image while eliminating the decrease in brightness
associated with a matte or diffuse finish on the light input side
of the film. Also, there is a need for a single layer of film which
can redirect a portion of the light traveling in a plane parallel
to the refracting surfaces in a grooved film, that would be
brighter than a single layer of film using prismatic or lenticular
grooves. In addition, there is a need for a light redirecting film
that can compensate for the different angular distributions of
light that may exist for a particular light source at different
positions above the source, such as backlights used to illuminate
liquid crystal displays. Also, there is a need for a light
redirecting film system in which the film is matched or tuned to
the light output distribution of a backlight or other light source
to reorient or redirect more of the incident light from the
backlight within a desired viewing angle.
SUMMARY OF THE INVENTION
The present invention relates to light redirecting films and light
redirecting film systems that redistribute more of the light
emitted by a backlight or other light source toward a direction
more normal to the plane of the films, and to light redirecting
films that produce a softer image without the brightness decrease
associated with films that have a matte or diffuse finish on the
light entrance surface of the films, for increased
effectiveness.
The light exit surface of the films has a pattern of discrete
individual optical elements of well defined shape for refracting
the incident light distribution such that the distribution of light
exiting the films is in a direction more normal to the surface of
the films. These individual optical elements may be formed by
depressions in or projections on the exit surface of the films, and
include one or more sloping surfaces for refracting the incident
light toward a direction normal to the exit surface. These sloping
surfaces may for example include a combination of planar and curved
surfaces that redirect the light within a desired viewing angle.
Also, the curvature of the surfaces, or the ratio of the curved
area to the planar area of the individual optical elements as well
as the perimeter shapes of the curved and planar surfaces may be
varied to tailor the light output distribution of the films, to
customize the viewing angle of the display device used in
conjunction with the films. In addition, the curvature of the
surfaces, or the ratio of the curved area to the planar area of the
individual optical elements may be varied to redirect more or less
light that is traveling in a plane that would be parallel to the
grooves of a prismatic or lenticular grooved film. Also the size
and population of the individual optical elements, as well as the
curvature of the surfaces of the individual optical elements may be
chosen to produce a more or less diffuse output or to randomize the
input light distribution from the light source to produce a softer
more diffuse light output distribution while maintaining the output
distribution within a specified angular region about the direction
normal to the films.
The light entrance surface of the films may have an optical coating
such as an antireflective coating, a reflective polarizer, a
retardation coating or a polarizer. Also a matte or diffuse texture
may be provided on the light entrance surface depending on the
visual appearance desired. A matte finish produces a softer image
but is not as bright.
The individual optical elements on the exit surface of the films
may be randomized in such a way as to eliminate any interference
with the pixel spacing of a liquid crystal display. This
randomization can include the size, shape, position, depth,
orientation, angle or density of the optical elements. This
eliminates the need for diffuser layers to defeat moire and similar
effects. Also, at least some of the individual optical elements may
be arranged in groupings across the exit surface of the films, with
at least some of the optical elements in each of the groupings
having a different size or shape characteristic that collectively
produce an average size or shape characteristic for each of the
groupings that varies across the films to obtain average
characteristic values beyond machining tolerances for any single
optical element and to defeat moire and interference effects with
the pixel spacing of a liquid crystal display. In addition, at
least some of the individual optical elements may be oriented at
different angles relative to each other for customizing the ability
of the films to reorient/redirect light along two different
axes.
The angles that the light redirecting surfaces of the individual
optical elements make with the light exit surface of the films may
also be varied across the display area of a liquid crystal display
to tailor the light redirecting function of the films to a light
input distribution that is non-uniform across the surface of the
light source.
The individual optical elements of the light redirecting films also
desirably overlap each other, in a staggered, interlocked and/or
intersecting configuration, creating an optical structure with
excellent surface area coverage. Moreover, the individual optical
elements may be arranged in groupings with some of the individual
optical elements oriented along one axis and other individual
optical elements oriented along another axis. Also, the orientation
of the individual optical elements in each grouping may vary.
Further, the size, shape, position and/or orientation of the
individual optical elements of the light redirecting films may vary
to account for variations in the distribution of light emitted by a
light source.
The properties and pattern of the optical elements of light
redirecting films may also be customized to optimize the light
redirecting films for different types of light sources which emit
different light distributions, for example, one pattern for single
bulb laptops, another pattern for double bulb flat panel displays,
and so on.
Further, light redirecting film systems are provided in which the
orientation, size, position and/or shape of the individual optical
elements of the light redirecting films are tailored to the light
output distribution of a backlight or other light source to
reorient or redirect more of the incident light from the backlight
within a desired viewing angle. Also, the backlight may include
individual optical deformities that collimate light along one axis
and the light redirecting films may include individual optical
elements that collimate light along another axis perpendicular to
the one axis.
To the accomplishment of the foregoing and related ends, the
invention, then, comprises the features hereinafter more fully
described and particularly pointed out in the claims, the following
description and annexed drawings setting forth in detail certain
illustrative embodiments of the invention, these being indicative,
however, of but several of the various ways in which the principles
of the invention may be employed.
BRIEF DESCRIPTION OF THE DRAWINGS
In the annexed drawings:
FIG. 1 is a schematic side elevation view of one form of light
redirecting film system in accordance with the present
invention;
FIG. 2 is an enlarged fragmentary side elevation view of a portion
of the backlight and light redirecting film system of FIG. 1;
FIGS. 3 and 4 are schematic side elevation views of other forms of
light redirecting film systems of the present invention;
FIGS. 5-20 are schematic perspective or plan views showing
different patterns of individual optical elements on light
redirecting films of the present invention;
FIGS. 5a-5n are schematic perspective views of different geometric
shapes that the individual optical elements on the light
redirecting films may take;
FIG. 21 is a schematic perspective view of a light redirecting film
having optical grooves extending across the film in a curved
pattern facing a corner of the film;
FIG. 22 is a top plan view of a light redirecting film having a
pattern of optical grooves extending across the film facing a
midpoint on one edge of the film that decreases in curvature as the
distance from the one edge increases;
FIG. 23 is an end elevation view of the light redirecting film of
FIG. 22 as seen from the left end thereof;
FIG. 24 is a side elevation view of the light redirecting film of
FIG. 22;
FIGS. 25 and 26 are enlarged schematic fragmentary plan views of a
surface area of a backlight/light emitting panel assembly showing
various forms of optical deformities formed on or in a surface of
the backlight;
FIGS. 27 and 28 are enlarged longitudinal sections through one of
the optical deformities of FIGS. 25 and 26, respectively;
FIGS. 29 and 30 are enlarged schematic longitudinal sections
through other forms of optical deformities formed on or in a
surface of a backlight;
FIGS. 31-39 are enlarged schematic perspective views of backlight
surface areas containing various patterns of individual optical
deformities of other well defined shapes;
FIG. 40 is an enlarged schematic longitudinal section through
another form of optical deformity formed on or in a surface of a
backlight;
FIGS. 41 and 42 are enlarged schematic top plan views of backlight
surface areas containing optical deformities similar in shape to
those shown in FIGS. 37 and 38 arranged in a plurality of straight
rows along the length and width of the surface areas;
FIGS. 43 and 44 are enlarged schematic top plan views of backlight
surface areas containing optical deformities also similar in shape
to those shown in FIGS. 37 and 38 arranged in staggered rows along
the length of the surface areas;
FIGS. 45 and 46 are enlarged schematic top plan views of backlight
surface areas containing a random or variable pattern of different
sized optical deformities on the surface areas;
FIG. 47 is an enlarged schematic perspective view of a backlight
surface area showing optical deformities increasing in size as the
distance of the deformities from the light input surface increases
or intensity of the light increases along the length of the surface
area;
FIGS. 48 and 49 are schematic perspective views showing different
angular orientations of the optical deformities along the length
and width of a backlight surface area; and
FIGS. 50 and 51 are enlarged perspective views schematically
showing how exemplary light rays emitted from a focused light
source are reflected or refracted by different individual optical
deformities of well defined shapes of a backlight surface area.
DETAILED DESCRIPTION OF THE INVENTION
FIGS. 1 and 2 schematically show one form of light redirecting film
system 1 in accordance with this invention including a light
redirecting film 2 that redistributes more of the light emitted by
a backlight BL or other light source toward a direction more normal
to the surface of the film. Film 2 may be used to redistribute
light within a desired viewing angle from almost any light source
for lighting, for example, a display such as a liquid crystal
display, used in laptop computers, word processors, avionic
displays, cell phones, PDAs and the like, to make the displays
brighter. The liquid crystal display can be any type including a
transmissive liquid crystal display D as schematically shown in
FIGS. 1 and 2, a reflective liquid crystal display D.sup.I as
schematically shown in FIG. 3 and a transflective liquid crystal
display D.sup.II as schematically shown in FIG. 4.
The reflective liquid crystal display D' shown in FIG. 3 includes a
back reflector 42 adjacent the back side for reflecting ambient
light entering the display back out the display to increase the
brightness of the display. The light redirecting film 2 of the
present invention is placed adjacent the top of the reflective
liquid crystal display to redirect ambient light (or light from a
front light) into the display toward a direction more normal to the
plane of the film for reflection back out by the back reflector
within a desired viewing angle to increase the brightness of the
display. Light redirecting film 2 may be attached to, laminated to
or otherwise held in place against the top of the liquid crystal
display.
The transflective liquid crystal display D.sup.II shown in FIG. 4
includes a transreflector T placed between the display and a
backlight BL for reflecting ambient light entering the front of the
display back out the display to increase the brightness of the
display in a lighted environment, and for transmitting light from
the backlight through the transreflector and out the display to
illuminate the display in a dark environment. In this embodiment
the light redirecting film 2 may either be placed adjacent the top
of the display or adjacent the bottom of the display or both as
schematically shown in FIG. 4 for redirecting or redistributing
ambient light and/or light from the backlight more normal to the
plane of the film to make the light ray output distribution more
acceptable to travel through the display to increase the brightness
of the display.
Light redirecting film 2 comprises a thin transparent film or
substrate 8 having a pattern of discrete individual optical
elements 5 of well defined shape on the light exit surface 6 of the
film for refracting the incident light distribution such that the
distribution of the light exiting the film is in a direction more
normal to the surface of the film.
Each of the individual optical elements 5 has a width and length
many times smaller than the width and length of the film, and may
be formed by depressions in or projections on the exit surface of
the film. These individual optical elements 5 include at least one
sloping surface for refracting the incident light toward the
direction normal to the light exit surface. FIG. 5 shows one
pattern of individual optical elements 5 on a film 2. These optical
elements may take many different shapes. For example, FIG. 5a shows
one of the optical elements 5 of FIG. 5 which is a non-prismatic
optical element having a total of two surfaces 10, 12, both of
which are sloping. One of the surfaces 10 shown in FIG. 5a is
planar or flat whereas the other surface 12 is curved. Moreover,
both surfaces 10, 12 intersect each other and also intersect the
surface of the film. Alternatively, both surfaces 10', 12' of the
individual optical elements 5' may be curved as schematically shown
in FIG. 5b.
Alternatively, the optical elements may each have only one surface
that is curved and sloping and intersects the film. FIG. 5c shows
one such optical element 5.sup.II in the shape of a cone 13,
whereas FIG. 5d shows another such optical element 5.sup.III having
a semispherical or dome shape 14. Also, such optical elements may
have more than one sloping surface intersecting the film.
FIG. 5e shows an optical element 5.sup.IV having a total of three
surfaces, all of which intersect the film and intersect each other.
Two of the surfaces 15 and 16 are curved, whereas the third surface
17 is planar.
FIG. 5f shows an optical element 5.sup.V in the shape of a pyramid
18 with four triangular shaped sides 19 that intersect each other
and intersect the film. The sides 19 of the pyramid 18 may all be
of the same size and shape as shown in FIG. 5f, or the sides
19.sup.I of the pyramid 18.sup.I may be stretched so the sides of
the optical element 5.sup.VI have different perimeter shapes as
shown in FIG. 5g. Also, the optical elements may have any number of
planar sloping sides. FIG. 5h shows an optical element 5.sup.VII
with four planar sloping sides 20, whereas FIG. 5i shows an optical
element 5.sup.VIII with eight planar sloping sides 20.sup.I.
The individual optical elements may also have more than one curved
and more than one planar sloping surface, all intersecting the
film. FIG. 5j shows an optical element 5.sup.IX having a pair of
intersecting oppositely sloping planar sides 22 and oppositely
rounded or curved ends or sides 23. Further, the sloping planar
sides 22.sup.I and 22.sup.II and curved ends or sides 23.sup.I and
23.sup.II of optical elements 5.times. and 5.sup.xi may have
different angled slopes as shown in FIGS. 5k and 5l. Moreover, the
optical elements may have at least one curved surface that does not
intersect the film. One such optical element 5.sup.XII is shown in
FIG. 5m which includes a pair of oppositely sloping planar sides
22.sup.III and oppositely rounded or curved ends or sides
23.sup.III and a rounded or curved top 24 intersecting the
oppositely sloping sides and oppositely rounded ends. Further, the
optical elements 5.sup.XIII may be curved along their length as
shown in FIG. 5n.
Providing the individual optical elements with a combination of
planar and curved surfaces redirects or redistributes a larger
viewing area than is possible with a grooved film. Also, the
curvature of the surfaces, or the ratio of the curved area to the
planar area of the individual optical elements may be varied to
tailor the light output distribution of the film to customize the
viewing area of a display device used in conjunction with the
film.
The light entrance surface 7 of the film 2 may have an optical
coating 25 (see FIG. 2) such as an antireflective coating, a
reflective polarizer, a retardation coating or a polarizer. Also, a
matte or diffuse texture may be provided on the light entrance
surface 7 depending on the visual appearance desired. A matte
finish produces a softer image but is not as bright. The
combination of planar and curved surfaces of the individual optical
elements of the present invention may be configured to redirect
some of the light rays impinging thereon in different directions to
produce a softer image without the need for an additional diffuser
or matte finish on the entrance surface of the film.
The individual optical elements of the light redirecting film also
desirably overlap each other in a staggered, interlocked and/or
intersecting configuration, creating an optical structure with
excellent surface area coverage. FIGS. 6, 7, 13 and 15, for
example, show optical elements 5.sup.XIV, 5.sup.XV, 5.sup.XVI, and
5.sup.XVII of light redirecting films 2.sup.I, 2.sup.II, 2.sup.III
and 2.sup.IV staggered with respect to each other; FIGS. 8-10 show
the optical elements 5.sup.XVIII, 5.sup.XIX and 5.sup.XX of light
redirecting films 2.sup.V, 2.sup.VI and 2.sup.VII intersecting each
other; and FIGS. 11 and 12 show the optical elements intersecting
5.sup.XXI and 5.sup.XXII of light redirecting films 2.sup.VIII and
2.sup.IX interlocking each other.
Moreover, the slope angle, density, position, orientation, height
or depth, shape, and/or size of the optical elements of the light
redirecting film may be matched or tuned to the particular light
output distribution of a backlight BL or other light source to
account for variations in the distribution of light emitted by the
backlight in order to redistribute more of the light emitted by the
backlight within a desired viewing angle. For example, the angle
that the sloping surfaces (e.g., surfaces 10, 12) of the optical
elements 5 make with the surface of the light redirecting film 2
may be varied as the distance from the backlight BL from a light
source 26 increases to account for the way the backlight emits
light rays R at different angles as the distance from the light
source increases as schematically shown in FIG. 2. Also, the
backlight BL itself may be designed to emit more of the light rays
at lower angles to increase the amount of light emitted by the
backlight and rely on the light redirecting film to redistribute
more of the emitted light within a desired viewing angle. In this
way the individual optical elements of the light redirecting film
may be selected to work in conjunction with the optical
deformations of the backlight to produce an optimized output light
ray angle distribution from the system.
FIGS. 2, 5 and 9 show different patterns of individual optical
elements all of the same height or depth, whereas FIGS. 7, 8, 10,
13 and 14 show different patterns of individual optical elements of
different shapes, sizes and height or depth. The individual optical
elements 5.sup.XXIII of the light redirecting film 2.sup.X of FIG.
14 are also shown arranged in alternating rows along the width or
length of the film.
The individual optical elements 5.sup.XXV and 5.sup.XXVI may also
be randomized on the film 2.sup.XI and 2.sup.XII as schematically
shown in FIGS. 16 and 17 in such a way as to eliminate any
interference with the pixel spacing of a liquid crystal display.
This eliminates the need for optical diffuser layers 30 shown in
FIGS. 1 and 2 to defeat moire and similar effects. Moreover, at
least some of the individual optical elements may be arranged in
groupings 32, 32.sup.I and 32.sup.II across the film, with at least
some of the optical elements in each grouping having a different
size or shape characteristic that collectively produce an average
size or shape characteristic for each of the groupings that varies
across the film as schematically shown in FIGS. 7, 13 and 15 to
obtain characteristic values beyond machining tolerances to defeat
moire and interference effects with the liquid crystal display
pixel spacing. For example, at least some of the optical elements
in each grouping may have a different depth or height that
collectively produce an average depth or height characteristic for
each grouping that varies across the film. Also, at least some of
the optical elements in each grouping may have a different slope
angle that collectively produce an average slope angle for each
grouping that varies across the film. Further, at least one sloping
surface of the individual optical elements in each grouping may
have a different width or length that collectively produce an
average width or length characteristic in each grouping that varies
across the film.
Where the individual optical elements include a combination of
planar and curved surfaces, for example planar and curved surfaces
10.sup.II, 12.sup.II, 10.sup.III, 12.sup.III and 10.sup.IV,
12.sup.IV as shown in FIGS. 7, 13 and 15, respectively, the
curvature of the curved surfaces, or the ratio of the curved area
to the planar area of the individual optical elements as well as
the perimeter shapes of the curved and planar surfaces may be
varied to tailor the light output distribution of the film. In
addition, the curvature of the curved surfaces, or the ratio of the
curved area to the planar area of the individual optical elements
may be varied to redirect more or less light that is traveling in a
plane that would be parallel to the grooves of a prismatic or
lenticular grooved film, partially or completely replacing the need
for a second layer of light redirecting film. Also, at least some
of the individual optical elements may be oriented at different
angles relative to each other as schematically shown in FIGS. 13
and 16 to redistribute more of the light emitted by a light source
along two different axes in a direction more normal to the surface
of the film, partially or completely replacing the need for a
second layer of light redirecting film. However, it will be
appreciated that two layers of such light redirecting film each
having the same or different patterns of individual optical
elements thereon may be placed between a light source and viewing
area with the layers rotated 90 degrees (or other angles greater
than 0 degrees and less than 90 degrees) with respect to each other
so that the individual optical elements on the respective film
layers redistribute more of the light emitted by a light source
traveling in different planar directions in a direction more normal
to the surface of the respective films.
Also, the light redirecting film 2.sup.IV may have a pattern of
optical elements 5.sup.XVII that varies at different locations on
the film as schematically shown in FIG. 15 to redistribute the
light ray output distribution from different locations of a
backlight or other light source to redistribute the light ray
output distribution from the different locations toward a direction
normal to the film.
Further, the properties and pattern of the optical elements of the
light redirecting film may be customized to optimize the light
redirecting film for different types of light sources which emit
different light distributions, for example, one pattern for single
bulb laptops, another pattern for double bulb flat panel displays,
and so on.
FIG. 17 shows the optical elements 5.sup.XXVI arranged in a radial
pattern from the outside edges of the film 2.sup.XII toward the
center to redistribute the light ray output distribution of a
backlight BL that receives light from cold cathode fluorescent lamp
26.sup.I along all four side edges of the backlight.
FIG. 18 shows the optical elements 5.sup.XXVII arranged in a
pattern of angled groupings 32.sup.III across the film 2 that are
tailored to redistribute the light ray output distribution of a
backlight BL that receives light from one cold cathode fluorescent
lamp 26.sup.I or a plurality of light emitting diodes 26.sup.II
along one input edge of the backlight.
FIG. 19 shows the optical elements 5.sup.XXVIII arranged in a
radial type pattern facing a corner of the film 2.sup.XIV to
redistribute the light ray output distribution of a backlight BL
that is corner lit by a light emitting diode 26.sup.II. FIG. 20
shows the optical elements 5.sup.XXIX arranged in a radial type
pattern facing a midpoint on one input edge of the film 2.sup.XV to
redistribute the light ray output distribution of a backlight BL
that is lighted at a midpoint of one input edge of the backlight by
a single light emitting diode 26.sup.II.
FIG. 21 shows a light redirecting film 2.sup.XVI having optical
grooves 35 extending across the film in a curved pattern facing a
corner of the film to redistribute the light ray output
distribution of a backlight BL that is corner lit by a light
emitting diode 26.sup.II, whereas FIGS. 22-24 show a light
redirecting film 2.sup.XVII having a pattern of optical grooves
35.sup.I extending across the film facing a midpoint along one edge
of the film that decreases in curvature as the distance from the
one edge increases to redistribute the light ray output
distribution of a backlight BL that is edge lit by a light emitting
diode 26.sup.II at a midpoint of one input edge of the
backlight.
Where the light redirecting film has a pattern 40 of optical
elements 5 thereon that varies along the length of the film, a roll
41 of the film may be provided having a repeating pattern of
optical elements thereon as schematically shown in FIG. 15 to
permit a selected area of the pattern that best suits a particular
application to be die cut from the roll of film.
The backlight BL may be substantially flat, or curved, or may be a
single layer or multi-layers, and may have different thicknesses
and shapes as desired. Moreover, the backlight may be flexible or
rigid, and be made of a variety of compounds. Further, the
backlight may be hollow, filled with liquid, air, or be solid, and
may have holes or ridges.
Also, the light source 26 may be of any suitable type including,
for example, an arc lamp, an incandescent bulb which may also be
colored, filtered or painted, a lens end bulb, a line light, a
halogen lamp, a light emitting diode (LED), a chip from an LED, a
neon bulb, a cold cathode fluorescent lamp, a fiber optic light
pipe transmitting from a remote source, a laser or laser diode, or
any other suitable light source. Additionally, the light source 26
may be a multiple colored LED, or a combination of multiple colored
radiation sources in order to provide a desired colored or white
light output distribution. For example, a plurality of colored
lights such as LEDs of different colors (e.g., red, blue, green) or
a single LED with multiple color chips may be employed to create
white light or any other colored light output distribution by
varying the intensities of each individual colored light.
A pattern of optical deformities may be provided on one or both
sides of the backlight BL or on one or more selected areas on one
or both sides of the backlight as desired. As used herein, the term
optical deformities means any change in the shape or geometry of a
surface and/or coating or surface treatment that causes a portion
of the light to be emitted from the backlight. These deformities
can be produced in a variety of manners, for example, by providing
a painted pattern, an etched pattern, machined pattern, a printed
pattern, a hot stamp pattern, or a molded pattern or the like on
selected areas of the backlight. An ink or print pattern may be
applied for example by pad printing, silk printing, inkjet, heat
transfer film process or the like. The deformities may also be
printed on a sheet or film which is used to apply the deformities
to the backlight. This sheet or film may become a permanent part of
the backlight for example by attaching or otherwise positioning the
sheet or film against one or both sides of the backlight in order
to produce a desired effect.
By varying the density, opaqueness or translucence, shape, depth,
color, area, index of refraction or type of deformities on or in an
area or areas of the backlight, the light output of the backlight
can be controlled. The deformities may be used to control the
percent of light output from a light emitting area of the
backlight. For example, less and/or smaller size deformities may be
placed on surface areas where less light output is wanted.
Conversely, a greater percentage of and/or larger deformities may
be placed on surface areas of the backlight where greater light
output is desired.
Varying the percentages and/or size of deformities in different
areas of the backlight is necessary in order to provide a
substantially uniform light output distribution. For example, the
amount of light traveling through the backlight will ordinarily be
greater in areas closer to the light source than in other areas
further removed from the light source. A pattern of deformities may
be used to adjust for the light variances within the backlight, for
example, by providing a denser concentration of deformities with
increased distance from the light source thereby resulting in a
more uniform light output distribution from the backlight.
The deformities may also be used to control the output ray angle
distribution from the backlight to suit a particular application.
For example, if the backlight is used to backlight a liquid crystal
display, the light output will be more efficient if the deformities
(or a light redirecting film is used in combination with the
backlight) direct the light rays emitted by the backlight at
predetermined ray angles such that they will pass through the
liquid crystal display with low loss. Additionally, the pattern of
optical deformities may be used to adjust for light output
variances attributed to light extractions of the backlight. The
pattern of optical deformities may be printed on the backlight
surface areas utilizing a wide spectrum of paints, inks, coatings,
epoxies or the like, ranging from glossy to opaque or both, and may
employ half-tone separation techniques to vary the deformity
coverage. Moreover, the pattern of optical deformities may be
multiple layers or vary in index of refraction.
Print patterns of optical deformities may vary in shapes such as
dots, squares, diamonds, ellipses, stars, random shapes, and the
like. Also, print patterns of sixty lines per inch or finer are
desirably employed. This makes the deformities or shapes in the
print patterns nearly invisible to the human eye in a particular
application, thereby eliminating the detection of gradient or
banding lines that are common to light extracting patterns
utilizing larger elements. Additionally, the deformities may vary
in shape and/or size along the length and/or width of the
backlight. Also, a random placement pattern of the deformities may
be utilized throughout the length and/or width of the backlight.
The deformities may have shapes or a pattern with no specific
angles to reduce moire or other interference effects. Examples of
methods to create these random patterns are printing a pattern of
shapes using stochastic print pattern techniques, frequency
modulated half tone patterns, or random dot half tones. Moreover,
the deformities may be colored in order to effect color correction
in the backlight. The color of the deformities may also vary
throughout the backlight, for example, to provide different colors
for the same or different light output areas.
In addition to or in lieu of the patterns of optical deformities,
other optical deformities including prismatic or lenticular grooves
or cross grooves, or depressions or raised surfaces of various
shapes using more complex shapes in a mold pattern may be molded,
etched, stamped, thermoformed, hot stamped or the like into or on
one or more surface areas of the backlight. The prismatic or
lenticular surfaces, depressions or raised surfaces will cause a
portion of the light rays contacted thereby to be emitted from the
backlight. Also, the angles of the prisms, depressions or other
surfaces may be varied to direct the light in different directions
to produce a desired light output distribution or effect. Moreover,
the reflective or refractive surfaces may have shapes or a pattern
with no specific angles to reduce moire or other interference
effects.
A back reflector 42 may be attached or positioned against one side
of the backlight BL as schematically shown in FIGS. 1 and 2 in
order to improve light output efficiency of the backlight by
reflecting the light emitted from that side back through the
backlight for emission through the opposite side. Additionally, a
pattern of optical deformities 50 may be provided on one or both
sides of the backlight as schematically shown in FIGS. 1 and 2 in
order to change the path of the light so that the internal critical
angle is exceeded and a portion of the light is emitted from one or
both sides of the backlight.
FIGS. 25-28 show optical deformities 50.sup.I, 50.sup.II which may
either be individual projections 51 on the respective backlight
surface areas 52 or individual depressions 53 in such surface areas
52.sup.I of a backlight BI.sup.I, BL.sup.II. In either case, each
of these optical deformities has a well defined shape including a
reflective or refractive surface 54, 54.sup.I (hereafter sometimes
collectively referred to as a reflective/refractive surface) that
intersects the respective backlight surface area 52, 52.sup.I at
one edge 55, 55.sup.I and has a uniform slope throughout its length
for more precisely controlling the emission of light by each of the
deformities. Along a peripheral edge portion 56, 56.sup.I of each
reflective/refractive surface 54, 54.sup.I is an end wall 57,
57.sup.I of each deformity that intersects the respective panel
surface area 52, 52.sup.I at a greater included angle I, I.sup.I
than the included angle I.sup.II, I.sup.III between the
reflective/refractive surfaces 54, 54.sup.I and the panel surface
area 52, 52.sup.I (see FIGS. 27 and 28) to minimize the projected
surface area of the end walls on the panel surface area. This
allows more deformities to be placed on or in the panel surface
areas than would otherwise be possible if the projected surface
areas of the end walls 57, 57.sup.I were substantially the same as
or greater than the projected surface areas of the
reflective/refractive surfaces 54, 54.sup.I.
In FIGS. 25 and 26 the peripheral edge portions 56, 56.sup.I of the
reflective/refractive surfaces 54, 54.sup.I and associated end
walls 57, 57.sup.I are curved in the transverse direction. Also in
FIGS. 27 and 28 the end walls 57, 57.sup.I of the deformities are
shown extending substantially perpendicular to the
reflective/refractive surfaces 54, 54.sup.I of the deformities.
Alternatively, such end walls may extend substantially
perpendicular to the panel surface areas 52, 52.sup.I as
schematically shown in FIGS. 29 and 30. This virtually eliminates
any projected surface area of the end walls on the panel surface
areas whereby the density of the deformities on the panel surface
areas may be even further increased.
The optical deformities may also be of other well defined shapes to
obtain a desired light output distribution from a panel surface
area. FIG. 31 shows individual light extracting deformities 58 on a
panel surface area 52.sup.III each including a generally planar,
rectangular reflective/refractive surface 59 and associated end
wall 60 of a uniform slope throughout their length and width and
generally planar side walls 61. Alternatively, the deformities
58.sup.I may have rounded or curved side walls 62 on a panel
surface area 52.sup.IV as schematically shown in FIG. 32.
FIG. 33 shows individual light extracting deformities 63 on a panel
surface area 52.sup.V each including a planar, sloping triangular
shaped reflective/refractive surface 64 and associated planar,
generally triangularly shaped side walls or end walls 65. FIG. 34
shows individual light extracting deformities 66 on a panel surface
area 52.sup.VI each including a planar sloping
reflective/refractive surface 67 having angled peripheral edge
portions 68 and associated angled end and side walls 69 and 70.
FIG. 35 shows individual light extracting deformities 71 on a panel
surface area 52.sup.VII which are generally conically shaped,
whereas FIG. 36 shows individual light extracting deformities 72 on
a panel surface area 52.sup.VIII each including a rounded
reflective/refractive surface 73 and rounded end walls 74 and
rounded or curved side walls 75 all blended together. These
additional surfaces will reflect or refract other light rays
impinging thereon in different directions to spread light across
the backlight/panel member BL to provide a more uniform
distribution of light emitted from the panel member.
Regardless of the particular shape of the reflective/refractive
surfaces and end and side walls of the individual deformities, such
deformities may also include planar surfaces intersecting the
reflective/refractive surfaces and end and/or side walls in
parallel spaced relation to the panel surface areas 52. FIGS. 37-39
show deformities 76, 77 and 78 in the form of individual
projections on a panel surface area 52.sup.IX, 52.sup.X, 52.sup.XI
having representative shapes similar to those shown in FIGS. 31, 32
and 35, respectively, except that each deformity is intersected by
a planar surface 79, 79.sup.I, 79.sup.II in parallel spaced
relation to the panel surface area. In like manner, FIG. 40 shows
one of a multitude of deformities 80 in the form of individual
depressions 81 in a panel surface area 52.sup.XII each intersected
by a planar surface 79.sup.III in parallel spaced relation to the
general planar surface of the panel surface area. Any light rays
that impinge on such planar surfaces at internal angles less than
the critical angle for emission of light from the panel surface
area will be internally reflected by the planar surfaces, whereas
any light rays impinging on such planar surfaces at internal angles
greater than the critical angle will be emitted by the planar
surfaces with minimal optical discontinuities, as schematically
shown in FIG. 40.
Where the deformities are projections on the panel surface area,
the reflective/refractive surfaces extend at an angle away from the
panel in a direction generally opposite to that in which the light
rays from the light source 26 travel through the panel as
schematically shown in FIGS. 27 and 29. Where the deformities are
depressions in the panel surface area, the reflective/refractive
surfaces extend at an angle into the panel in the same general
direction in which the light rays from the light source 26 travel
through the panel member as schematically shown in FIGS. 28 and
30.
Regardless of whether the deformities are projections or
depressions on or in the panel surface areas, the slopes of the
light reflective/refractive surfaces of the deformities may be
varied to cause the light rays impinging thereon to be either
refracted out of the light emitting panel or reflected back through
the panel and emitted out the opposite side of the panel which may
be etched to diffuse the light emitted therefrom or covered by a
light redirecting film to produce a desired effect. Also, the
pattern of optical deformities on the panel surface area may be
uniform or variable as desired to obtain a desired light output
distribution from the panel surface areas. FIGS. 41 and 42 show
deformities 76.sup.I and 77.sup.I similar in shape to those shown
in FIGS. 37 and 38 arranged in a plurality of generally straight
uniformly spaced apart rows along the length and width of a panel
surface area 52.sup.XIII, 52.sup.XIV, whereas FIGS. 43 and 44 show
such deformities 76.sup.II and 77.sup.II arranged in staggered rows
that overlap each other along the length of a panel surface area
52.sup.XV, 52.sup.XVI.
Also, the size, including the width, length and depth or height as
well as the angular orientation and position of the optical
deformities may vary along the length and/or width of any given
panel surface area to obtain a desired light output distribution
from the panel surface area. FIGS. 45 and 46 show a random or
variable pattern of different size deformities 58.sup.II,
58.sup.III similar in shape to those shown in FIGS. 31 and 32,
respectively, arranged in staggered rows on a panel surface area
52.sup.XVII, 52.sup.XVIII, whereas FIG. 47 shows deformities
77.sup.III similar in shape to those shown in FIG. 38 increasing in
size as the distance of the deformities from the light source
increases or intensity of the light decreases along the length
and/or width of the panel surface area 52.sup.XIX. The deformities
are shown in FIGS. 45 and 46 arranged in clusters 82, 82.sup.I
across the panel surface, with at least some of the deformities in
each cluster having a different size or shape characteristic that
collectively produce an average size or shape characteristic for
each of the clusters that varies across the panel surface. For
example, at least some of the deformities in each of the clusters
may have a different depth or height or different slope or
orientation that collectively produce an average depth or height
characteristic or average slope or orientation of the sloping
surface that varies across the panel surface. Likewise at least
some of the deformities in each of the clusters may have a
different width or length that collectively produce an average
width or length characteristic that varies across the panel
surface. This allows one to obtain a desired size or shape
characteristic beyond machinery tolerances, and also defeats moire
and interference effects.
FIGS. 48 and 49 schematically show different angular orientations
of optical deformities 85, 85.sup.I of any desired shape along the
length and width of a panel surface area 52.sup.XX, 52.sup.XXI of a
light emitting panel assembly backlight. In FIG. 48 the deformities
are arranged in straight rows 86 along the length of the panel
surface area but the deformities in each of the rows are oriented
to face the light source 26 so that all of the deformities are
substantially in line with the light rays being emitted from the
light source. In FIG. 49 the deformities 85.sup.I are also oriented
to face the light source 26 similar to FIG. 48. In addition, the
rows 87 of deformities in FIG. 49 are in substantial radial
alignment with the light source 26.
FIGS. 50 and 51 schematically show how exemplary light rays 90,
90.sup.I emitted from a focused light source 26 insert molded or
cast within a light transition area 91, 91.sup.I of a light
emitting panel assembly backlight BL.sup.III, BL.sup.IV in
accordance with this invention are reflected during their travel
through the light emitting panel member 92, 92.sup.I until they
impinge upon individual light extracting deformities 50.sup.III,
77.sup.IV of well defined shapes on or in a panel surface area
52.sup.XXII, 52.sup.XXIII causing more of the light rays to be
reflected or refracted out of one side 93, 93.sup.I of the panel
member than the other side 94, 94.sup.I. In FIG. 50 the exemplary
light rays 90 are shown being reflected by the
reflective/refractive surfaces 54.sup.III of the deformities
50.sup.III in the same general direction out through the same side
93 of the panel member, whereas in FIG. 51 the light rays 90.sup.I
are shown being scattered in different directions within the panel
member 92.sup.I by the rounded side walls 62.sup.I of the
deformities 77.sup.IV before the light rays are reflected/refracted
out of the same side 93.sup.I of the panel member. Such a pattern
of individual light extracting deformities of well defined shapes
in accordance with the present invention can cause 60 to 70% or
more of the light received through the input edge 95.sup.I of the
panel member to be emitted from the same side of the panel
member.
From the foregoing, it will be apparent that the light redirecting
films of the present invention redistribute more of the light
emitted by a backlight or other light source toward a direction
more normal to the plane of the films. Also, the light redirecting
films and backlights of the present invention may be tailored or
tuned to each other to provide a system in which the individual
optical elements of the light redirecting films work in conjunction
with the optical deformities of the backlights to produce an
optimized output light ray angle distribution from the system.
Although the invention has been shown and described with respect to
certain embodiments, it is obvious that equivalent alterations and
modifications will occur to others skilled in the art upon the
reading and understanding of the specification. In particular, with
regard to the various functions performed by the above described
components, the terms (including any reference to a "means") used
to describe such components are intended to correspond, unless
otherwise indicated, to any component which performs the specified
function of the described component (e.g., that is functionally
equivalent), even though not structurally equivalent to the
disclosed component which performs the function in the herein
illustrated exemplary embodiments of the invention. In addition,
while a particular feature of the invention may have been disclosed
with respect to only one embodiment, such feature may be combined
with one or more other features of other embodiments as may be
desired and advantageous for any given or particular
application.
* * * * *